Dynamoelectric machines, such as motors and generators, are employed in a wide variety of industrial and commercial applications. Some types of motors employ a stator to set up a magnetic field which produces a rotational torque in current-carrying conductors of a rotor, causing the rotor to rotate. This rotation of the rotor is used to perform work.
Motors which run on alternating current, such as induction motors, typically employ an electromagnetic stator which includes a core of ferromagnetic material and windings of wire embedded in slots in the core. Energizing the stator by running an AC current through the windings produces a magnetic field in the vicinity of the stator. Turbine generators may also utilize a core of ferromagnetic material with windings of wire embedded in slots in the core.
Problems arise in motor design due to the necessity for the windings to have end turn portions which connect the embedded portions of different slots. These end winding portions are a source of stator flux leakage, (i.e., magnetic flux that is produced by the windings that is not utilized to produce a torque in the rotor). This stator flux leakage reduces efficiency of motors or other electric machines having such end winding portions. It will be appreciated that it is highly desirable to achieve improvements in the efficiency of dynamo-electric machines.
Prior attempts have been made to reduce stator flux leakage by designing the slots in the stator core to make the end winding turns smaller. Such designs attack the problem of stator flux leakage by making the non-productive region of the windings smaller, but do not provide for making the end winding turns productive for producing torque to turn the rotor.
Another problem arising from the necessity for end winding turns is that the turns are subject to electrodynamic and mechanical forces that tend to displace the end windings relative to the stator. Electric,dynamic forces causing displacement of the turns in a motor, for example, are induced by large currents passing through the coils during starting and peak load conditions. Mechanical forces are caused by normal mechanical vibrations developed due to rotation of the parts of the motor during operation. It has long been recognized that such displacement of the end turns has an undesirable effect of destroying the winding insulation in the end turns, leading to premature failure of the motor. Accordingly, numerous methods have been employed in the prior art for securing the end winding turns against movement relative to the stator. However, these conventional methods do not address the problem of stator flux leakage, but rather are simply directed to securing the end windings.
From the foregoing it can be appreciated that there is a need for a dynamoelectric machine having reduced stator flux leakage, and which makes more productive use of the end turns of the windings. It would further be desirable for the end winding turns to be supported to limit their displacement relative to the stator.